Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$49.65	11.811%	$55.5142	$55.51	$55.50	$55.50
Purchase #2	$69.39	3.217%	$71.6223	$71.62	$71.60	$71.60
Purchase #3	$81.77	13.560%	$92.858	$92.86	$92.85	$92.90
Purchase #4	$14.54	8.186%	$15.7302	$15.73	$15.75	$15.70
Purchase #5	$68.51	6.255%	$72.7953	$72.80	$72.80	$72.80
Purchase #6	$34.70	7.352%	$37.2511	$37.25	$37.25	$37.30
Purchase #7	$231.62	10.501%	$255.9424	$255.94	$255.95	$255.90
7 purchase totals =	$550.18		$601.7135	$601.71	$601.70	$601.70